The circumstellar disk, envelope, and bi-polar outflow of the Massive Young Stellar Object W33A - Astrophysics > Solar and Stellar AstrophysicsReportar como inadecuado




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Abstract: The Young Stellar Object YSO W33A is one of the best known examples of amassive star still in the process of forming. Here we present Gemini NorthALTAIR-NIFS laser-guide star adaptive-optics assisted K-band integral-fieldspectroscopy of W33A and its inner reflection nebula. In our data we make thefirst detections of a rotationally-flattened outer envelope and fast bi-polarjet of a massive YSO at near-infrared wavelengths. The predominant spectralfeatures observed are Br-gamma, H 2, and a combination of emission andabsorption from CO gas. We perform a 3-D spectro-astrometric analysis of theline emission, the first study of its kind. We find that the object-s Br-gammaemission reveals evidence for a fast bi-polar jet on sub-milliarcsecond scales,which is aligned with the larger-scale outflow. The hybrid CO features can beexplained as a combination of hot CO emission arising in a disk close to thecentral star, while cold CO absorption originates in the cooler outer envelope.Kinematic analysis of these features reveals that both structures are rotating,and consistent with being aligned perpendicularly to both the ionised jet andthe large-scale outflow. Assuming Keplerian rotation, we find that thecircumstellar disk orbits a central mass of >10Msun, while the outer envelopeencloses a mass of ~15Msun. Our results suggest a scenario of a central staraccreting material from a circumstellar disk at the centre of a cool extendedrotating torus, while driving a fast bi-polar wind. These results thereforeprovide strong supporting evidence for the hypothesis that the formationmechanism for high-mass stars is qualitatively similar to that of low-massstars.



Autor: Ben Davies Leeds, RIT, Stuart L. Lumsden, Melvin G. Hoare, Rene D. Oudmaijer, Willem-Jan de Wit

Fuente: https://arxiv.org/







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